NEW YORK — It's New York City's version of American as apple pie: hot dogs, a heart-racing turn on the Cyclone or a scenic spin on the Wonder Wheel at Coney Island's historic amusement park on July Fourth.

But this year, an aging, swaying observation tower appears poised to scuttle the summer ritual, putting visitors' plans and merchants' hopes on a roller coaster ride of their own.

After concerns about the 275-foot-tall Astrotower abruptly shuttered the park Tuesday evening, the roller coaster, Ferris wheel and some other attractions remained idled Wednesday. The park's managers said they planned to remove part of the needlelike structure, making it unlikely the amusements could reopen Thursday.

"We're going to do everything we can to keep this park open," Buildings Commissioner Robert LiMandri said, but authorities said they needed to keep a chunk of it closed and even rope off part of Coney Island's famous boardwalk until they could be sure there was no danger.

While the beach, a carousel, some other amusements and Nathan's Famous — home of the July Fourth hot dog eating contest — were open, the developments had tourists trying to figure out whether to rejigger plans and vendors wishing they wouldn't have to.

"You've waited for a whole year. You just wait for this day," Victor Summers said as he stood next to the 3-D simulator ride he's operated in the shadow of the Astrotower since 1996.

"The Fourth of July — it's like Christmas for Coney Island."

The holiday cliffhanger centers on a spindle that has stood over Coney Island for nearly half a century, a beacon for a its beachfront entertainments and a memento of the space-race era in which many of them were built.

Installed in 1964, the Astrotower was a focal point of space-themed attractions that updated the beach resort and helped it endure tough years later on.

The tower was equipped with an observation car that looped around the top to offer visitors 360-degree views of the Atlantic Ocean and Brooklyn. It instantly became a New York classic — "the big bagel in the sky," a newspaper of the time called it, and the nickname stuck.

The structure closed to visitors in 2007, but the city made a point of saying the tower would remain when a new company took on the amusement park in 2010.

Now, a portion of it will be coming down, according to a statement from the operators of the amusement park, called Luna Park. They said late Wednesday it would happen as soon as possible, but a Thursday opening is seen as improbable.

The hullaballoo began Tuesday afternoon, when someone called the fire department, concerned that the tower was swaying. The park was evacuated and shut down hours before its usual closing time as a precaution.

The needlelike structure was built to give somewhat in the wind to withstand storms, such as Superstorm Sandy last year. But recent work to remove the now-unused observation car took weight off the tower's tip and allowed it to sway more than usual, LiMandri said.

Officials found it was moving about 1.5 feet at the top, approaching the threshold of what it can safely withstand, he said, declining to give an exact figure.

Mayor Michael Bloomberg said Wednesday morning initial assessments showed the tower was stable, and officials weren't yet certain but were optimistic. Some attractions, including the Coney Island Raceway and the B&B Carousell, reopened around noon.

But on Wednesday afternoon, police began closing down two blocks of the boardwalk and stretching tape around the block near the Astrotower, which shifted from time to time in the wind.

"I'm losing a ton of business. I understand it's safety purposes, but it's the wrong day," Billy Burke said as he closed up Paul's Daughter, the boardwalk hot dog stand where he has worked for 31 years. He'd bought triple the amount of supplies he lays in for a normal weekend.

But, he said, he understood the stakes.

"If that thing falls, it's going to be a disaster."

Burke and other locals are accustomed to seeing the structure waggle — "every year, people complain that it's moving," said Esther Sherman, who manages Lago Furniture across the street.

But some who had watched it Tuesday said they noticed the movement was more pronounced than normal.

"It's the first time I saw it swinging like that, back and forth. I was like, 'Oh, my God,'" said Tracy Mittleman, who has lived across the street all her 34 years.

And it was squeaking, "like it just wasn't oiled, like parts were rusting," added her mother, Noreen Mittleman, 53.

Nicole Purmal, the marketing manager at Luna Park, had said Wednesday morning that the structure "definitely has a measure of movement about her," but officials were hopeful at that point that the park would reopen later in the day.

Hallie Spurlock, 11, made their first visit to Coney Island Wednesday hoping all the attractions would be open, though they had heard about the tower's troubles the night before.

"Women of the flats stood guard over their thresholds while police attempted to eject them for failure to pay rent on the grounds on which the dwellings stand. A near-riot was halted when a second court order was served on police, ordering a stay of the ejections."